1. The Field of the Invention
This application relates to an apparatus and method for the treatment of deep vein thrombosis, and, more particularly, to devices for applying an external compressive force to the lower extremities to promote blood flow.
2. The Relevant Technology
Contraction and relaxation of the muscles of the calf is responsible for the majority of movement of blood out of the lower extremities through the veins, hence venous circulation becomes stagnant when the calf muscles are at rest, increasing risk for deep venous thrombosis (DVT).
Gravity likewise plays a role in venous circulation. Long periods of sitting or standing create pressure on the valves within the veins of the legs. Over time, these valves can break allowing blood to pool in the veins of the calf. This process known as deep venous insufficiency (DVI) is a lifelong disease process with no surgical solution.
To decrease the risk of venous thrombosis while hospitalized, segmental pressure devices have been created, such as the apparatus marketed under the trade name PLEXIPULSE. These devices are proven to lower incidence of clotting while immobile. However, these devices are bulky, non portable, and expensive, making them impractical for home use or daily wear. These devices are therefore ineffective for aiding in the prevention of DVI through daily use.
Patients with DVI may be treated using medical compression stockings, which are an elastic stocking with graded compression, such as compression stocking offered for sale under the trade name MEDIVEN. These stockings often cause patients discomfort due to the tight compression and thick material. The tight compression also causes the compression stockings to be difficult to put on, requiring in some instances aid from a mechanical device to put the stocking over the heel of the foot.
It is known that both DVI and DVT may be controlled by applying cyclical pressure to a person's lower extremities to aid in venous blood flow. Currently available devices use bulky, non-portable motors and include complex cuffs and bladders that wrap entirely around a person's leg. Devices of this type are not readily portable and are not meant to be worn during a person's normal daily activities. Examples of such devices are described in U.S. Pat. Nos. 5,263,473; 5,014,681 and 5,674,262.
Another example of such a device is described in U.S. Pat. No. 6,290,662, which describes a boot formed of an inelastic material which completely surrounds the foot and a single-chambered bladder is positioned within the boot. This device is cumbersome and does not permit a person to wear normal shoes. This oversight makes the device impractical for daily wear and will tend to lead to poor patient compliance. Furthermore, surrounding any extremity with a rigid inelastic material inhibits movement and gives no room for swelling thus inhibiting circulation and increasing the risk for DVT, as well as being painful to those with severe DVI and foot swelling.